1. Technical Field
Embodiments of the present invention relate to a liquid ejecting head that ejects liquid by driving a piezoelectric element and to a liquid ejecting apparatus that includes the liquid ejecting head.
2. Related Art
A liquid ejecting apparatus is an apparatus that includes a liquid ejecting head. For example, an ink jet printer and an ink jet plotter are examples of the liquid ejecting apparatus. Various types of liquid can be ejected from the liquid ejecting head.
Recently, the liquid ejecting apparatus has been also applied to or included in various manufacturing apparatuses because of the liquid ejecting apparatus has the advantage of being able to accurately impact or deposit very small amounts of liquid at a predetermined position. The liquid ejecting apparatus has been applied to or included in, for example, a display manufacturing apparatus, an electrode forming apparatus, and a chip manufacturing apparatus. The display manufacturing apparatus manufactures a color filter used in a liquid crystal display and the like. The electrode forming apparatus forms an electrode used in an organic Electro Luminescence (EL) display, a field emission display (FED), and the like. The chip manufacturing apparatus manufactures a biochip (biochemical element). Liquid type ink drops are ejected from a recording head for an image recording apparatus. A solution is ejected from a coloring material ejecting head for the display manufacturing apparatus. The solution contains a red (R) coloring material, a green (G) coloring material, and a blue (B) coloring material. Liquid type electrode material drops are ejected from an electrode material ejecting head for the electrode forming apparatus. A biological organic material solution is ejected from a biological organic material ejecting head for the chip manufacturing apparatus.
The liquid ejecting head is configured to introduce a liquid into a pressure chamber, and generate a pressure fluctuation in the liquid in the pressure chamber, so that the liquid may be ejected from a nozzle linked to the pressure chamber. A pressure generator causes the pressure fluctuation to occur in the liquid in the pressure chamber. A piezoelectric element is appropriately used as the pressure generator. The piezoelectric element is configured, for example, in such a manner that a lower electrode film, a piezoelectric layer, and an upper electrode film are respectively stacked and formed in order from a side near the pressure chamber using a film forming technology. The lower electrode film functions as an individual electrode provided in or for each pressure chamber. The piezoelectric layer is formed of lead zirconate titanate (PZT) and the like. The upper electrode film functions as or is formed as a common electrode which is common to a plurality of pressure chambers (for example JP-A-2009-172878). A portion of the piezoelectric film interposed between the upper electrode film and the lower electrode film is set to be an activation portion (active portion) that is deformed by applying a voltage to the electrode films. Such a piezoelectric element is formed on a vibrating plate which sub-divides the pressure chamber on one side (for example, a side opposite to a nozzle plate in which the nozzle is formed). The vibrating plate has flexibility and is deformed depending on or according to the deformation of the piezoelectric element.
If a piezoelectric element formed with a film shape is too thin, the piezoelectric element may be bended too much in a state where a driving voltage is not applied to an electrode film (an initial state). This may have an impact on the ability of effectively eject liquid from the pressure chamber. Thus, it is necessary to consider that such a piezoelectric element is suppressed from excessively bending, that a neutral axis of the piezoelectric element is held at an appropriate position and that a vibrating plate may be thick. With such a structure, it is possible to make the piezoelectric element have rigidity in an activation portion (active portion) and to suppress the piezoelectric element from excessively bending in the initial state. However, if the vibrating plate is thick, a portion on which a piezoelectric layer is not stacked in an area corresponding to a pressure chamber has an excessive thickness. In this case, deformation of the vibrating plate is prevented at the portion corresponding to the pressure chamber on which the piezoelectric layer is not stacked. Accordingly, the pressure fluctuation may be insufficiently transferred to liquid in the pressure chamber.